DESCRIPTION (Adapted from Applicant s Description): Orthopedic surgery in the form of muscle tendon lengthenings or releases has been a mainstay of treatment for motor dysfunction in cerebral palsy (CP) for many decades. While evidence from case studies, historical reviews, retrospective analyses and prospective observational cohort studies has suggested that surgery is generally effective in reducing impairments, with small to moderate functional benefits noted as well, no randomized clinical trials have documented the efficacy of the approach. In fact, the true effects of the intervention on disability and patient satisfaction have not been explored. These issues are particularly crucial in a chronic condition where the effects of an intervention are likely to be modest since the underlying pathophysiology persists despite a reduction in impairments. An additional consideration is that the confounding effects of physical growth and maturation on the course of this disorder are not known, and may account for some of the positive functional effects seen over time that were attributed to the intervention. Resolving these issues will require a rigorous study design that includes a randomized control group. Implementation of this design has been problematic due to the strong desire of families for treatment and ethical concerns of clinicians regarding withholding treatments or prescribing a treatment that they "believe" to be less or not effective. The specific aim of this proposal is to design a medically important and ethically sound phase III clinical trial evaluating the efficacy of orthopedic surgery in CP. The most widely performed muscle-tendon procedure, tendo-achilles lengthening, will be investigated in the largest patient subgroup, ambulatory children with spastic diplegia. A network of 15 pediatric orthopedic surgeons who specialize in the care of children with CP from 8 centers around the US has been assembled along with experts in health evaluation, clinical trial planning, biostatistics, and database development and management for the purpose of designing this efficacy study. Once implemented, this definite trial may serve as a model for further rehabilitative research to establish the singular and relative efficacy of the multiple interventions intended to improve motor function and lessen disability for individuals with CP and other chronic neuromotor conditions.